1. Field of Invention
The present invention relates to a valved discharge mechanism for a fluid discharge mechanism of a refrigerant compressor used in an automotive air conditioning system.
2. Description of the Related Art
Valved discharge mechanisms for refrigerant compressors are known in the art. For example, FIGS. 1 and 2 depict a discharge valve mechanism used in a refrigerant compressor as described in U.S. Pat. No. 5,120,205 to Ban et al. As disclosed therein, a refrigerant compressor includes a compressor housing defining a compression chamber in which successive strokes of intake, compression, and discharge of a refrigerant gas are repeatedly performed. The compressor further includes housing 10 comprising front end plate 11 and cup-shaped casing 12, which is disposed on a rear surface of front end plate 11. Opening 111 is formed in a center of front end plate 11 for the penetration of drive shaft 17. Annular projection 112 is formed on the rear surface of front end plate 11 and faces cup-shaped casing 12. An outer peripheral surface of annular projection 112 fits into an inner wall surface of an opening portion of cup-shaped casing 12. Cup-shaped casing 12 is fixed on the rear end surface of front end plate 11 by a fastening member, such a plurality of bolts (not shown), so that the opening portion of cup-shaped casing 12 is covered by front end plate 11. O-ring member 14 is disposed between the outer peripheral surface of annular projection 112 and an inner wall surface of cup-shaped casing 12, to form a seal between the surfaces of front end plate 11 and cup-shaped casing 12.
Front end plate 11 has an annular sleeve portion 18 projecting from a front surface thereof for surrounding drive shaft 17 to define a shaft seal cavity. Drive shaft 17 is rotatably supported by annular sleeve portion 18 through bearing 16 disposed within a front end portion of annular sleeve portion 18. Disk portion 21 is formed at an inner end portion of drive shaft 17. Disk portion 21 is rotatably supported by front end plate 11 through bearing 22 which is disposed within opening 111 of front end plate 11. Shaft seal assembly 15 is assembled on drive shaft 17 within the shaft seal cavity of annular sleeve portion 18. Pulley 20 is rotatably supported by annular sleeve portion 18 through bearing 19, which is disposed on an outer surface of annular sleeve portion 18. Electromagnetic coil 23 is fixed on the outer surface of annular sleeve portion 18 by support plate 221 and is received in an annular cavity of pulley 20. Armature plate 24 is elastically supported by an outer end portion of drive shaft 17 which extends from annular sleeve portion 18. A magnetic clutch comprising pulley 20, electromagnetic coil 23, and armature plate 24 is thereby formed.
Drive shaft 17 is driven by an external power source, for example, the engine of an automobile, through a force-transmitting means, such as the magnetic clutch described above. Fixed scroll member 26, orbiting scroll member 27, crank-type driving mechanism 25 of orbiting scroll member 26, and rotation preventing mechanism 28 of orbiting scroll member 27 are disposed in an inner chamber of cup-shaped casing 12. Fixed scroll member 26 includes circular end plate 261, spiral element 262, affixed to and extending from a front surface of circular end plate 261, and a plurality of internally threaded bosses 265 projecting axially from a rear end surface of circular end plate 261. An end surface of each boss 265 is seated on an inner surface of end plate portion 121 of cup-shaped casing 12 and is fixed to end plate portion 121 by bolts 29.
Fixed scroll member 26 is fixedly disposed within cup-shaped casing 12. Circular end plate 261 of fixed scroll member 26 partitions the inner chamber of cup-shaped casing 12 into discharge chamber 36 and suction chamber 41 by seal ring 42 which is disposed between an outer peripheral surface of circular end plate 261 and the inner wall surface of cup-shaped casing 12. Orbiting scroll member 27 is disposed within suction chamber 41 and comprises circular end plate 271 and spiral element 272 affixed to and extending from a front surface of circular end plate 271. Spiral element 272 of orbiting scroll 27 and spiral element 262 of fixed scroll 26 interfit with an angular and radial offset. At least one pair of fluid pockets are thereby defined between spiral elements 262 and 272. Orbiting scroll member 27 is connected to crank-type driving mechanism 25 and rotation preventing mechanism 28 which effect the orbital radius RO (not shown) by the rotation of drive shaft 17, to thereby compress fluid that is passing through the compressor. Each spiral element 262 and 272 is provided with groove 30 formed on an axial end surface thereof. Seal element 301 is loosely fitted within groove 30. Sealing between the axial end surface of each spiral element 262 and 272 and a respective surface of an opposite end plate is effected by seal element 301.
As described above, when orbiting scroll member 27 is driven, line contacts between spiral elements 262 and 272 shift along the spiral curved surfaces of spiral elements 262 and 272 so that fluid pockets move to the center of spiral elements 262 and 272.
Therefore, fluid or refrigerant gas that is introduced into suction chamber 41 from an external fluid circuit through inlet port 52 on cup-shaped casing 12 is drawn into the fluid pockets that are formed between spiral elements 262 and 272. As orbiting scroll member 27 orbits, fluid in the fluid pockets moves to the center of spiral elements 262 and 272 with a consequent reduction in volume. Compressed fluid is discharged into discharge chamber 36 from the fluid pockets at the center of spiral elements 262 and 272 through discharge hole 263, which is formed in circular end plate 262 of fixed scroll member 26 at a position near the center of spiral element 262. The compressed fluid is discharged from discharge chamber 36 though outlet port 53 formed on cup-shaped casing 12 to an external fluid circuit, e.g., a cooling circuit.
Compression chamber 41 communicates with discharge chamber 36 through discharge hole 263. The discharge valve assembly includes discharge reed valve 31 and valve retainer 32, both of which are secured to a rear surface 264 of fixed scroll 26 by fixing bolt 51. Valve seat 264a is integrally formed in rear surface 264 of circular end plate 261 of fixed scroll 26 around discharge hole 263. Discharge reed valve 31, which is made of an elastic material, regulates the flow of the refrigerant gas and remains seated against valve seat 264a of rear surface 264 without an air gap when the compressor is not in operation.
Valve retainer 32 limits the bending movement of discharge reed valve 31 in a direction away from rear surface 264. Discharge reed valve 31 bends away from rear surface 264, opening discharge hole 263 and establishing a communication path between compression chamber 41 and discharge chamber 36. Discharge reed valve 31 has a spring constant which allows discharge reed valve 263 to keep discharge hole 263 closed until the pressure in the compression chamber reaches a predetermined value. Specifically, when the pressure differential between compression chamber 41, which is filled with compression gas caused by spiral elements 26 and 27, and discharge chamber 36 increases, the discharge reed 31 is bent away from rear surface 264, clearing discharge hole 263, and allowing the discharge of compressed gas from compression chamber 41 to discharge chamber 36. As the gas is discharged, the pressure differential between decreases, allowing discharge reed valve 31 to straighten and close discharge hole 263 while preventing the backflow of gas from discharge chamber 36 to compression chamber 41. Discharge reed valve 31 repeats the bending and straightening movement to open and close discharge hole 263 in a short period of time.
The elastic modulus of discharge reed valve 31 causes discharge reed valve 31 to strike valve seat 264a when it straightens. This striking generates additional vibration and noise in the compressor. Further, the repeated striking causes fatigue in discharge reed valve 31.
The operation of the compressor also causes discharge reed valve 31 to vibrate. This vibration leads to pulsed fluid delivery through discharge hole 263 during the operation of the compressor, in addition to other disadvantages.